1. Field of the Invention
The invention relates to an activating device, and more particularly to a cordless activating device attached to a venetian blind to raise or lower a venetian blind without using an external pull-cord.
2. Description of Related Art
With reference to FIGS. 11 to 13, a conventional cordless activating device in accordance with the prior art for a venetian blind, which has a top side and a bottom side attached to a bottom of the venetian blind. The conventional cordless activating device comprises a cord winding assembly and a brake assembly (20).
The cord winding assembly comprises a string winding device (12) and a spring winding device (14). The string winding device (12) has an extension shaft (122) and two string spools (126). The extension shaft (122) has two ends (not numbered) and a middle section (not numbered) and is non-circular and preferably polygonal. The two string spools (126) are mounted respectively on the two ends of the extension shaft (122) to wind or unwind two strings (not shown) attached to a top rail (not shown) of a venetian blind (not shown).
The spring winding device (14) is mounted on the middle section of the extension shaft (122) and has a figure 8-shaped housing (141), an S-shaped drive spring (142), a drive spool (144) and at least one ratchet wheel (146). The figure 8-shaped housing (141) has a take-up chamber (not numbered), a positioning post (1412) and a drive chamber (not numbered). The positioning post (1412) is formed inside the take-up chamber. The drive spool (144) has two ends (not numbered), two protruding non-circular keys (not numbered) and a non-circular through hole (not numbered) corresponding to the non-circular extension shaft (122), is mounted rotatably inside the drive chamber of the S-shaped housing (141) and is mounted securely on a center segment of the extension shaft (122). The S-shaped drive spring (142) is mounted inside the figure 8-shaped housing (141) and has a stationary end (not numbered) attached to the positioning post (1412) and a rotating end attached to the driving spool (144). The drive spring (142) is wound on the position post (1412) when the venetian blind is in an up position against the top rail and causes the extension shaft (122) to rotate and wind the strings respectively onto the two spools (126) to move the venetian blind upward. Each ratchet wheel (146) has a central keyed through hole (not numbered) and is mounted around the middle section of the extension shaft (122). The ratchet wheels (146) are attached respectively to protrude non-circular keys on the drive spool (144).
The brake assembly (20) comprises a mounting bracket (21), an activating grip (22) and two springs (23).
The mounting bracket (21) holds the string winding assembly, has two posts (211) and is mounted transversely to the extension rod (122) and in line with the figue 8-shaped housing (141). The posts (211) are parallel and adjacent respectively to the sides of the figure 8-shaped housing (141).
The activating grip (22) is U-shaped, mounted slidably on the mounting bracket (21) and has an inner face (not numbered), two distal ends (not numbered), two blind holes (224) and two pawls (222). The two blind holes (224) are defined respectively and longitudinally in the two distal ends and slidably hold the posts (211) on the mounting bracket (21). The two pawls (222) are formed on the inner face respectively near the two distal ends to selectively engage the ratchet wheels (146).
The springs (23) are mounted respectively around the posts (211) between the mounting bracket (21) and the distal ends of the activating grip (22). The springs (23) press the activating grip (22), cause the pawls (222) to engage the corresponding ratchet wheels (146), keep the extension shaft (122) and string spools (126) from rotating and hold the venetian blind in position when the activating grip (22) is released.
With particular reference to FIG. 13, the pawls (222) detach from the ratchet wheels (146) when the activating grip (22) is pressed toward the mounting bracket (21) so the extension shaft (122) can rotate and take-up or let out the strings to adjust the Venetian blind. After the venetian blind is adjusted, the activating grip (22) is released, and the pawls (222) engage the ratchet wheels (124) again to keep the extension shaft (122) from rotating so the venetian blind is held in position.
However, the conventional cordless activating device for a venetian blind still has some drawbacks. For example, the extension shaft (122) in the string winding assembly is thin and long so that the extension shaft (122) easily breaks during rotation especially when the venetian blind is very wide, which cause a strong torsional force to be applied to the string spools (124). Therefore, the conventional cordless activating device is not durable.
The present invention has arisen to provide a cordless activating device mounted on a venetian blind, which eliminates or obviates the drawbacks of the conventional cordless activating device.